In a known print head, heaters serving as energy generating elements are arranged on a substrate in two arrays. One supply port is formed between the heater arrays so as to penetrate the substrate. Thus, ink is supplied, through the supply port, to pressure chambers in which the respective heaters are arranged.
FIG. 1A is a partly sectional perspective view showing a main part of such a conventional print head. FIG. 1B is a view which is similar to FIG. 1A but from which an orifice plate 502 shown in FIG. 1A is omitted. As shown in FIG. 1A, a substrate 503 is provided with a plurality of heaters 509, driving circuits 509b for driving the heaters 509, and logic circuits 509c configured to determine whether to allow the driving circuits to turn on or off ejection. Furthermore, the orifice plate 502 is laid on top of the substrate 503 to form ejection openings 506, pressure chambers 508 (FIG. 1B), and channels 507 (FIG. 1B), which correspond to the individual heaters 509. In this manner, the two arrays of the heaters (the arrays of the pressure chambers and channels) are provided on the substrate, and the ink supply port 505 is formed as a hole located between the heater arrays and extending along the heater arrays and through the substrate. Thus, ink fed from an ink tank via the supply port 505 is supplied to the individual channels 507 and pressure chambers 508, arranged on the both sides of the supply port, in conjunction with an ink ejecting operation.
FIG. 2 is a plan view showing a substrate on which six units of arrays of heaters (and ejection openings) are provided; one unit of arrays of heaters is shown in FIGS. 1A and 1B. The one unit of arrays corresponds to one type of ink. Thus, FIG. 2 shows the basic configuration of the print head configured to eject six types of ink, for example, cyan, magenta, yellow, light cyan and magenta having lower color material concentrations, and black. As shown in FIG. 2, two power supply electrodes 510 are provided so as to sandwich the supply port 505 between the electrodes 510, with the heater arrays arranged on the both sides of the supply port 505. That is, each of the two power supply electrodes 510, which is configured to receive external power via electrodes 511, supplies power to drive the heater array on the same side as that of the power supply electrode with respect to the supply port 505. Furthermore, the driving circuit 509b drives the heater array on the same side as that of the driving circuit 509b with respect to the supply port 505.
FIG. 3A is a plan view showing an example of the configuration of the above-described print head, particularly of the ejection openings (heaters), pressure chambers, and channels. FIG. 3B is a sectional view taken along line IIIB-IIIB in FIG. 3A. Moreover, FIG. 3C is a plan view of the configuration shown in FIG. 3A and to which driving circuits, power supply wirings, and heaters are added. FIG. 3D is an enlarged view of an area in FIG. 3C which is shown by a dashed line. In the print head configured as shown in these figures, a part of the space formed between the substrate 503 and the orifice plate 502 functions as a common liquid chamber 504. The liquid supply port 505 communicates with the common liquid chamber 504. Furthermore, the individual channels 507 extend in communication with the common liquid chamber 504. The pressure chamber 508 is formed at an end of each of the channels 507 which is opposite to the common liquid chamber 504. Each of the ejection openings 506 are formed in the orifice plate 502 so as to communicate with the corresponding pressure chamber 508. The heater 509 is located at a position in the pressure chamber which corresponds to the ejection opening 506. Ink supplied to the common liquid chamber 504 via the liquid supply port 505 is fed to the pressure chambers 508 via the respective channels 507. In each of the pressure chambers 508, the heater 509 supplies thermal energy to the ink. Based on the supply of the thermal energy, the ink is ejected through the ejection opening 506.
As shown in FIGS. 3C and 3D, for each of the heater arrays on the both sides of the supply port 505, a power supply-heater wiring 510a connecting the power supply wiring 510 and the heater 509 together and a heater-driving circuit wiring 510b connecting the heater 509 and the driving circuit 509b together are provided for each heater.
FIGS. 4A to 4D are views showing another conventional example of a print head described in PTL1. This print head is different from that shown in FIGS. 3A to 3D in that the former has an increased ejection opening arrangement density. More specifically, the ejection openings (and corresponding heaters, pressure chambers, and the like) are staggered and thus densely arranged. This has the advantage of being able to inhibit an increase in the size of the print head, particularly of the substrate, thus reducing the manufacture costs of the print head.
As shown in FIGS. 4A to 4D, on the substrate 503, two arrays each comprising a plurality of units each including the heater 509, the pressure chamber 508, and the channel 507 are provided on the respective both sides of the supply port 505. The units in each of the two arrays are alternately arranged at a long distance and a short distance from the supply port 505. Thus, compared to the configuration in which the same number of the units are simply arranged in a line along the longitudinal direction of the supply port 505, the configuration shown in FIGS. 4A to 4D allows an increase in arrangement density. This enables an increase in the number of units disposed on a substrate of the same size. In this case, the scales of the driving circuit 509 and the logic circuit (not shown in the drawings) need to be increased by amounts corresponding to the increased number of ejection openings. However, the area occupied by the circuits can be reduced compared to that in the case where two arrays are provided each of which comprises the supply port, heaters, driving circuits, and logic circuits (not shown in the drawings) as shown in FIG. 3. That is, the arrangement area required for two supply ports in the individual arrangement of the units can be reduced to almost half, thus enabling a reduction in substrate area. Furthermore, compared to the arrangement in which the units are simply arranged along the longitudinal direction of the supply port 505, the staggered arrangement of the units including the ejection openings provides a sufficient thickness for each partition wall 512 configured to partition the channels. This prevents the reliability of the print head from being degraded.
In the above-described configuration of the ejection openings (heaters), pressure chambers, and channels, each of the power supply-heater wiring 510a and the heater-driving circuit wiring 510b has two types of layout lengths.